A turn-of-the-century architectural marvel built on healing mineral springs and salt licks.

The longest navigable underground river in the United States is home to countless blind and albino animals.

The only freestanding table rock formation east of the Mississippi.

The chiseled jaw of this forgotten American hero still stands tall in a small Indiana town.

The lynching and burial site of America's first train robbers.

For over 100 years, this Indiana town has had a tree growing out the top of the local courthouse.

A castle built by an eccentric medieval enthusiast in suburban Ohio.

An unusual, super-sized grocery adventure awaits in an Ohio suburb.

A memorial for an outsider theorist who believed that the planet is actually hollow.

This bridge uses an inverted bowstring truss and is believed to be the only of its kind in the United States.

The largest ancient burial mound in Ohio.

A headstone tells the sad story of a lost little boy and his pet dog.

A miniature world of concrete and stone in Springfield, Ohio.

Plaques on its facade commemorate the Tiber's most destructive deluges.

Take a drunken tour inside the world's largest known geode.

For decades, this waterfall remained hidden because of an artificial dam.

An elegant sandstone stairway built by the WPA still connects two neighborhoods in Akron.

The mortal remains of an estimated 70,000 people lie in the basement of a monastery in Lima, Peru.

An Inca spa, military outpost or maybe… both?

Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

A painting in the historic Cathedral Basilica depicts Jesus and his disciples dining on a traditional Peruvian menu.

Rows of 19th-century brick ovens used to process coal into coke form the center of a wooded park.